Device for controlling printing position

Abstract: The control device is characterized by including a linear encoder (1) for storing two pieces of information on two phases about a printing position in one storing part (11) located on a longitudinal axis of the linear encoder, reading means (12) for reading the pieces of information on two phases stored in the storing part (11) of the linear encoder (1), and control circuits (19 to 25) for controlling a printing position based on the informations on two phases read by the reading means (12).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention: The present invention relates to a device for controlling a printing position which device is used for a printer device, and more particularly to the device for controlling a printing position which device provides a control circuit so that the control circuit may control one linear encoder to store two pieces of information about an absolute position at a magnetization period of a minimum resolution and an integer-fold magnetization period of a minimum resolution for controlling the printing position in the printer. The present device may be used for an ink-jet printer, a thermal printer, a facsimile, or a wire-dot printer. 2. Description of the Related Art: Fig. 3 is a view showing a conventional linear encoder for storing two pieces of information on two phases. Fig. 4 is a schematic section showing the linear encoder shown in Fig. 3. In Figs. 3 and 4, 1 denotes a linear encoder (magnetic memory type). 2 denotes a linear encoder element (MR head unit). 3 denotes a first sensing head for sensing a printing position. 4 denotes a second sensing head for sensing a carriage position. 5 denotes a first magnetizing part for storing information about a printing position. 6 denotes a second magnetizing part for storing information about a carriage position. 7 denotes a magnetic memory part. 8 denotes a slide metal. The linear encoder stores the information about a printing position at the first magnetizing part 5 and the information about a carriage position at the second magnetizing part 6, the first magnetizing part 5 being different in pitch from the second magnetizing part 6, that is, two kinds of informations being stored in two storage parts located on the longitudinal axis of the linear encoder. The two kinds of position information are sensed by the first and the second sensing elements provided in the slide metal 8 of the MR head part 2, respectively. As mentioned above, the conventional linear encoder is required to keep a considerable degree of accuracy about sensing positions around the slide metal so that the first sensing head may match in position to the first magnetizing part and the second sensing head may match in position to the second magnetizing part for obtaining the position information. Further, for the first and the second magnetizing parts, that is, for sensing the stored informations on two phases, the first and the second two heads are required, which results in making the overall device more costly. Prior art document EP-A-0 463 561 discloses an optical incremental type rotary encoder for obtaining high resolution by calculating two-phase sine wave signals of the same period. Further, prior art document FR-A-2393355 describes a position control system for controlling the position from two pulse signals of the same period obtained through the slits on the disk. Finally, prior art document US-A-4 180 704 discloses an optical position sensing apparatus having a circuit for creating a clean wave from a signal output by compensating the threshold level which is varying in time and magnitude and in presence of DC leakage. SUMMARY OF THE INVENTION It is an object of the present invention to provide a device for controlling a printing position which is capable of sensing two pieces of information on two phases at one sensing operation and with one sensing element. To solve this object the present invention provides a device for controlling a printing position as specified in claim 1. Preferred embodiments of the invention are described in the subclaims. A device for controlling a printing position comprises a linear encoder for storing two pieces of information on two phases about a printing position in one storage part located on a longitudinal axis of the linear encoder, reading means movably located along the storage part of the linear encoder and for reading the pieces of information on two phases stored in the storage part of the linear encoder, and control circuits for controlling the printing position based on the informations on two phases read by the reading means. In the device for controlling a printing position according to the present invention, the linear encoder stores the two pieces of information on two phases about a printing position in one storage part located on the longitudinal axis. Hence, the informations on two phases are allowed to be read by just one reading means, which makes it possible to manufacture a device for controlling a printing position at low cost. The linear encoder stores informations on two phases about a printing position in one storage part located on a longitudinal axis of the linear encoder. Hence, the informations on two phases are allowed to be read by one reading means, so that the device for controlling a printing position may be manufactured at low cost. Further objects and advantages of the present invention will be apparent from the following description of the proffered embodiments of the invention as illustrated in the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing a control circuit according to an embodiment. Fig. 2 is a view for explaining reading of information from a linear encoder for storing informations on two phases. Fig. 3 is a view for explaining a conventional linear encoder for storing information on two phases. Fig. 4 is a schematic section showing the linear encoder shown in Fig. 3. DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 1 is a diagram showing a control circuit for controlling two pieces of information on two phases. Fig. 2 is a view for explaining reading of positional information from the linear encoder having the informations about a printing position and a carriage position stored (magnetized) thereon. In Fig. 2, 10 denotes one storage part located on a longitudinal axis of a linear encoder. 11 denotes a magnetizing (storing) part for storing information about a printing position at a magnetizing period of a minimum resolution. 12 denotes an MR head served as reading means. 13 denotes a magnetizing (storing) part for storing information about a carriage position stored at an integer-fold magnetizing period of a minimum resolution. 26 denotes a waveform of a signal read by the MR head 2 served as reading means. 17 denotes a waveform of a signal corresponding to the magnetizing part 11. 18 denotes a waveform of a signal at the magnetizing part 14. 15 denotes a threshold value about the magnetizing part 14. 16 denotes a threshold value about the magnetizing part 11. In Fig. 2, one of the informations on two phases is stored in the magnetizing part 11 and the other is stored in the magnetizing part 14 at an integer-fold interval from the normal magnetizing part 11. The force of magnetization provided in the magnetizing part 14 is stronger than that provided in the magnetizing part 11. When the MR head 12 is moved toward an arrow 13, the output signal 16 corresponding to the magnetizing parts 11 and 14 is allowed to be obtained. In Fig. 1, 24 and 25 denote comparators having respective threshold values. The signal 26 generated as the MR head is moved from the terminal 19 to the comparators 24 and 25 is inputted to the comparators 24 and 25 respectively. The comparator 24 holds a threshold value 16 set through the terminal 20 and the comparator 25 holds a threshold value 15 set through the terminal 21. When the signal 26 is inputted to both of the comparators 24 and 25, if the signal 26 is higher than each of their threshold values, that is, if the signal 26 is higher than the threshold value 16, the signal 17 is outputted at the output terminal 22 of the comparator 24 and if the signal 26 is higher than the threshold value 15, the signal 16 is outputted at the output terminal 23 of the comparator 25. Hence, the information about a printing position is obtained on the magnetizing part 11 and the information about a carriage position is obtained on the magnetizing part 14. As described above, the control of the printing position and the carriage position based on the information magnetized in one storing part of one linear encoder along one travel of one MR head are allowed to be realized with a simple arrangement and at low cost. The magnetizations on two phases are done once so as to keep a phase difference between the two phases highly accurate. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.

Claims: A device for controlling a printing position comprising a magnetic memory type linear encoder (1) for storing a piece of information about a printing position, reading means (12) movably located along said linear encoder for reading said piece of information and control circuits (19-25) for controlling a printing position based on said piece of information read by said reading means, characterized in that said linear encoder (1) includes a single linear storage part provided thereon and arranged parallel to a longitudinal axis of said linear encoder (1) for storing said piece of information on two different phases having a magnetizing period of a minimum resolution (11) and an integer-fold magnetizing period (14) of said minimum resolution, respectively, and that said reading means (12) includes a single reading head for outputting an output signal representative of said information on two phases. A device for controlling a printing position as claimed in claim 1, characterized in that force of magnetization about information stored at said integer-fold magnetizing period (14) is larger than force of magnetization about information stored at said magnetizing period of said minimum resolution (11). A device for controlling a printing position as claimed in claim 1 or 2, characterized in that said control circuits (19-25) includes a first comparator (25) connected to receive said output signal (19) and a first threshold values (15) for outputting a signal (23) representative of first information about a printing position based on said integer-fold magnetizing period (14) and a second comparator (24) connected to receive said output signal (19) and a second threshold values (16) for outputting a signal (22) representative of second information about a printing position based on said magnetizing period of said minimum resolution (11).

Inventors: KOBAYASHI KUNIHIRO, MASUDA KAZUYA, SUMIDA KOHICHI, KOBAYASHI, KUNIHIRO, MASUDA, KAZUYA, SUMIDA, KOHICHI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1994
Main classification: B41J19
IPC codes: B41J29, B41J19